As shown in FIG. 1, a postage meter 1 may comprise a user interface 10, a control logic unit 20, an input/output communication logic unit 30, a PSD 40, a gatekeeper 50 and a printing mechanism 60. The user interface 10 allows a customer to specify the postage amount of the indicium to be printed. The control logic unit 20, upon receiving a signal from the user interface 10, notifies a PSD 40 of the specified postage amount. The PSD 40 checks to see whether the funds stored therein are sufficient to pay for the postage. If so, the PSD 40 sends a signal indicative of the indicium to the gatekeeper 50. When the user activates the postage meter 1 with a mailpiece on which the indicium is to be printed, a trip signal 23, via the control logic unit 20, causes the gatekeeper 50 to transfer the postage amount from the PSD 40 to the printing mechanism 60. Subsequently the requested indicium is printed. Whereas the PSD 40 keeps track of the funds in a fund keeper 42 stored in the postage meter 1 and authorizes a portion of the stored funds to be used for the postage indicium, the most important function of the gatekeeper 50 is to maintain a secure connection between the PSD 40 and the printing mechanism 60.
When the funds level in the postage meter 1 is low, the postage meter can request a transfer of funds from the vault 82 and data center 80. The fund transfer and the refill request are indicated by a two-way arrow 35. With the input/output communication logic unit 30, a customer uses the interface 10 to request the transfer of funds from the data center 80. Alternatively, the postage meter 1 can be programmed to make such a request automatically when the fund level is low.
It should be noted that the vault 82 in the data center 80 is in fact an accounting system for keeping track of the funds transferred to each postage meter. When the funds in the data center are exhausted, the data center may request a fund transfer from an account in a bank 90. When a customer has prepaid a large amount of money in order to use one or more postage meters, it is possible that some of the prepaid amount is deposited in an interest-earning account in the bank 90 or the like when that amount is not transferred to the postage meters.